There may be at most one CUDA debugging session active per node at a time. A node cannot be shared for debugging CUDA code simultaneously by multiple user sessions, or multiple sessions by the same user. Use ps or other system utilities to determine if your session is conflicting with another debugging session.

The CUDA debugging environment uses FIFOs (named pipes) located in "/tmp" and named matching the pattern "cudagdb_pipe.N.N", where N is a decimal number. Occasionally, a debugging session might accidentally leave a set of pipes lying around. You may need to manually delete these pipes in order to start your CUDA debugging session:

If the pipes were leaked by another user, that user will own the pipes and you may not be able to delete them. In this case, ask the user or system administrator to remove them for you.

Occasionally, a debugging session might accidentally orphan a process. Orphaned processes might go compute bound or prevent you or other users from starting a debugging session. You may need to manually kill orphaned CUDA processes in order to start your CUDA debugging session or stop a compute-bound process. Use system tools such as ps or top to find the processes and kill them using the shell kill command. If the process were orphaned by another user, that user will own the processes and you may not be able to kill them. In this case, ask the user or system administrator to kill them for you.

We have seen problems debugging some multi-threaded CUDA programs on Fermi, where the CUDA debugging environment kills the debugger with an internal error (SIGSEGV). We are working with NVIDIA to resolve this problem.